Plant Molecular Biology

, Volume 28, Issue 3, pp 369–380 | Cite as

Isolation and characterisation of cDNA clones representing the genes encoding the major tuber storage protein (dioscorin) of yam (Dioscorea cayenensis Lam.)

  • R. Steven Conlan
  • Leslie-Ann Griffiths
  • Johnathan A Napier
  • Peter R Shewry
  • Sinclair Mantell
  • Charles Ainsworth
Research Article

Abstract

cDNA clones encoding dioscorins, the major tuber storage proteins (Mr 32000) of yam (Dioscorea cayenensis) have been isolated. Two classes of clone (A and B, based on hybrid release translation product sizes and nucleotide sequence differences) which are 84.1% similar in their protein coding regions, were identified. The protein encoded by the open reading frame of the class A cDNA insert is of Mr 30015. The difference in observed and calculated molecular mass might be attributed to glycosylation. Nucleotide sequencing and in vitro transcription/translation suggest that the class A dioscorin proteins are synthesised with signal peptides of 18 amino acid residues which are cleaved from the mature peptide. The class A and class B proteins are 69.6% similar with respect to each other, but show no sequence identity with other plant proteins or with the major tuber storage proteins of potato (patatin) or sweet potato (sporamin). Storage protein gene expression was restricted to developing tubers and was not induced by growth conditions known to induce expression of tuber storage protein genes in other plant species. The codon usage of the dioscorin genes suggests that the Dioscoreaceae are more closely related to dicotyledonous than to monocotyledonous plants.

Key words

yam Dioscorea cayenensis tuber storage protein dioscorin cDNA clones 

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Copyright information

© Kluwer Academic Publishers 1995

Authors and Affiliations

  • R. Steven Conlan
    • 1
    • 2
  • Leslie-Ann Griffiths
    • 1
  • Johnathan A Napier
    • 2
  • Peter R Shewry
    • 2
  • Sinclair Mantell
    • 3
  • Charles Ainsworth
    • 1
  1. 1.Plant Molecular Biology Laboratory, Department of Biological Sciences, Wye CollegeUniversity of LondonWyeUK
  2. 2.Department of Agricultural SciencesUniversity of Bristol, IACR Long Ashton Research StationBristolUK
  3. 3.Unit for Advanced Propagation Systems, Department of Horticulture, Wye CollegeUniversity of LondonWyeUK

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